Enzymatic digestion in stomachless fishes: how a simple gut accommodates both herbivory and carnivory

Abstract

The lack of a stomach is not uncommon amongst teleost fishes, yet our understanding of this reductive specialisation is lacking. The absence of a stomach does not restrict trophic preference, resulting in fishes with very similar alimentary morphology capable of digesting differing diets. We examined the digestive biochemistry of four beloniform fishes: two herbivorous halfbeaks (Hemiramphidae) and two carnivorous needlefish (Belonidae) to determine how these fishes digest their respective diets with their simple, short gut. We found that although the halfbeaks showed significantly greater α-amylase activity than that of the needlefish (P < 0.01), trypsin, lipase, aminopeptidase and maltase activity were not substantially different between the two families. We also found that habitat (freshwater vs. marine) appears to play a significant role in digestive capability, as the two freshwater taxa and the two marine taxa were significantly different (ANOSIM; dietary Gobal R = 0.544, P = 0.001, habitat Global R = 0.437, P = 0.001), despite their phyletic and dietary similarities. Our findings offer partial support for the adaptive modulation hypothesis, support the Plug-Flow Reactor model of digestion in herbivorous halfbeaks and also support the compartmental model of digestion but suggest that another model is required to describe stomachless carnivorous needlefish.

Evaluation of biofilm of Aeromonas hydrophila for oral vaccination of Channa striatus

“…The stomach environment in carnivore fish is quite different from that of herbivore and omnivore characterized by high acidity and intense activity by digestive enzymes [12,13,41]. And, the performance of oral vaccine heavily depends on the stomach environment.…”

“…Till today, we evaluated the biofilm oral vaccine in herbivore and omnivore fish. Therefore, information is required on performance of biofilm vaccine in a carnivore fish where the stomach environment is quite different from that of herbivorous carps and omnivore catfish [12,13,41]. Futhermore, antibody response was evaluated by agglutination titre.…”

Effects of temperature and feeding frequency on ingestion and growth for rare minnow

“…Indeed, adaptation was observed only 4 weeks after changes in feeding frequency in this study, possibly owing to the small size and short growth stage of our study species. Rare minnows have no stomach and the gut is short, and such fishes often possess a large appetite and tend to forage more frequently [56,61,62].…”

Digestive enzyme activities in the guts of bonnethead sharks ( Sphyrna tiburo ) provide insight into their digestive strategy and evidence for microbial digestion in their hindguts

“…Moreover, the patterns of enzymatic activity along a fish's 75 gut can provide insight into the digestive strategy taken by a fish to di-76 gest a given diet ( Fig. 2A; Skea et al, 2005Skea et al, , 2007Day et al, 2011;77 German, 2009;German and Bittong, 2009;German et al, in press). …”